Phantomed loaded circuit.



TE PHANTOMED LOADED CIRCUIT.

- APPLIUATION FILED 1 1:3.12. 1910.

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APPLIUATION FILED FEB. 12, 1910. 951 5 Patented 5m. 1m, 1911 I 2 SEEETSSHEET 2.

V 7UNITED STATES PATENT 0mm THOMAS SHAW,0F ET'ACKENSACK, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

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tain Improvements in Phantomed Loaded Circuits, of which the following is a specification;

In dealing with lines for the transmission of electrical signals, as telephone or telegraph li'n'es, loaded u on the- Pupin system, that? is, with in u'ctances distributed throughout the circuit and serving to diminish the attenuation of the signaling waves or impulses, it obviously may desirable to combine two or more transmitting circuits to form a third, or, as it is termed in telephony, phantom circuit. This is commonly eflected by employing in parallel the two limbs of a metallic circuit to furnish each side of the phantom, the impulses generated in either of the original or physical circuits and in the combined or phantom circuit being caused to act only upon their respective receiving instruments by means of a difi'erential repeating coil in a manner well known. It has. been found, however, that when the physical circuits are provided with the usual toroidal loading coils, in which the two line windings are upon opposite sides of a ring core, there is introduced into the phantom circuita loss of energy, appearing as directly measurable efiective resistance, which markedly impairs the cfliciency of transmission. The chief cause of this loss is-leakage of lines of force from the 'convolutions of the coils, where they give rise 'to useful inductance, into the unlamina-ted cast-iron cases, ordinarily em )loyed as inclosures. Here the magnetic ux produces eddy currents, which dissipate the energy as heat. This loss is negligible when the current flows serially in the two windings, with their mutual inductance aiding or being added to their self inductance, as

is the case in the original circuits, since the effect is of a continuous coil, and, if this is symmetrically distributed, no external field results. But the loss is considerable when the current in the phantom traverses the windings in parallel, with the mutual in ductance opposing the self inductance, for in this instance the two windings produce between them in the core adjacent portions of the same polarity fiiom which the lines of force stream into the case. As the to- Specifieation of Letters Patent.

Patented J an; 10, 1911.

Application filed February 12, 1910., Serial No. 543,539.

roidal coil has proved in practice to be the most compact and'efl'ec'tive which has-been designed, it is expedient to ,retain it, and the problem which this invention aims to solve is the elimination of the excessive energy losses from a phantom circuit, the component circuits of which are loaded with toroidal or similar coils.

The invention also contemplates an arrangement whereby the circuits are substan our in the loading coils. I

Figure 1 of the accompanying drawings tomed lines equipped-according to my system; Fig. '2 is an enlarged diagram illustrating one of the coils, employed; and Fig. 3 illustrates diagrammatically the distribution of the admittanccs in a coil.

Similar characters are. used to indicate like parts in all figures of the drawings.

The reference characters L and L designate, respectively, the opposite limbs of two metallic circuit telephone lines, each having terminal stations A, A. Near the extremieating coils C, to the center of one winding of each of which is joined a conductor L which continues to stations A .the phantom circuit furnished by the pairs of conductors L, L in parallel. Current from batteries I), there being a suflicient number to introduce the required amount of inductance.

constructed in the customary manner as a continuous ring, which for convenience in defining the inventionj is considered tohave opposite sections 10 and 10 about which the. windings are placed. But the core may or may not be continuous, and when its sections are referred to they are to be understood as consisting-of such opposite halves or portions. without referenceto thecondition of the magnetic circuit. The coils are inclosed in the usual iron cases indicated at 11.

In the present invention the windings for each side of the line consist of two sections of conductor with both windings encircling the entire core, thereheing a section of each winding upon each half core. Referring to either of the physical circuits, upon the core section 10 is a winding section 12 for the tially freed from crosstalk whichmight oc-' shows diagrammatically two loaded phanties of both lines are the usual simplex re-,

B is supplied to the physical and phantom. circuits through repeating coils C". Infbot-h" ,of the lines L, L are included loading coils Each coil may comprise a core of iron wire conductor L- of the line, and over the coresection is a winding section 12 belonging to the same line conductor, while the line conductor L includes opposite windings 13 and 13 To render the coil symmetrical in the relation of itswindings to one another and to the core, the sections are ofap arated therefrom by a layer 15 of insulation.

This may be best seen in Fig. 2 of the draw- 1 ing, where, to make the diagram more clear,

the conductors are shown as concentric'to the axis of the core; but it s to be understood that theyactually surround the .core

as appears in Fig. 1. It will be noted that Fig. 2 shows the inner and outer sections as having a different number of layers. This is for convenience in bringing out the terminals; the impedance of the sections may, in, spite of this, be made the same. The windings are of such length and direction and the sections are so connected that the desired inductanceis introduced into each side of the physical circuit, the effective resistance being about the same as in the standard loading coil; and, on account of the symmetricalarrangement of the sections of the windings, it will be evident that a very perfect balance as to inductance, capacity and resistance may be maintained between them. \Vhen its' effect upon the sides of the phantom is considered, it will be found that, since each winding embraces the entire core,

1' neither will produce an external held.

Therefore. the magnetic leakage is so reduced that but little energy is wasted in this way, and the effective resistance .imposed upon the phantom by this improved organization is slight. The inductance ofthe two windings in parallel is negligible, therefore the phantom circuit is not loaded.

Between the superposed windings of coils, and between. said windings and-the core and case, there tends to be an electrostatic transfer of energy, and consequently crosstalk affecting the phantom and its component circuits, as a result of the direct admittances between the elements. With respect to the admittances from winding to winding, these may substantially balance one another, but, unless specially uarded against, those to core and case. will be from points at different potentials and will act as bridges through which current flows. This capacity effect is practicallylocalized at the outside .of-the windings, that is, at the first potential.

andlast layers. Itherefore so dispose the sections of the windings that the layers inthe phantom circuit, while adjacent layers of the difl'erent sections are also at the same This is best illustrated in vFig. 3 of the drawings. In' this diagram the outer layers are represented as points and the admittances as condensers or capacities. In each winding the layers next to the core and case are succeeding portions at opposite sides of the junctures of the sections 12, 12 and 13, 13 The admittances from winding to winding are between ends of the windings similarly located in the circuit. As a result of this organization, the admittances are' perfectly balanced, and this, together with the otherwise symmetrical distribution of the windings previously mentioned, will eliminate crosstalk between the phantom circuit and the side in which the coil is, in-

serte It may be said generally of the improved formed one side, a resistance of 3.2 ohms and an inductance of 0.006- of a henry. A coil constructed and applied to the circuits as herein described, and consisting of the usual core of iron wire with ap roximately the same number of, turns of con uctor, gave the physical circuit under the same'current conditions an effective resistance of 8.3 ohms and an inductance of 0.174 of a henry,wliile there appeared in the phantom but 0.8.3 of an ohm and 0.000068 of a henry.

I claim:

1. The combination with two telephone lines, of means for producing a phantom circuit from said lines, and a loading-coil included in each of the component. lines of current of 800 microamperes at 800' s per second, has been found to ut loading coils for themetallic circuits com- "having sectional windings with each section associated to furnish a phantom circuit, and

prising a ring-shaped core about which is a sectional Winding included in each side of its circuit, the sections of the same winding being upon opposite halves of the core and one section belonging to each side of the circuit being surrounded by a section belonging to the other side.

4:. In a telephone system, line circuits associated to furnish a phantom circuit, and a loading coil for one of the circuits, said coil having sectional windings, the admittances between each section and other elements of the coil With respect to current in the phan; tom circuit being symmetrically distributed.

5. In a telephone system, line circuits associated to furnish a phantom circuit, and a loading coil for one of the circuits, said coil including a plurality of layers, portions of sections which are in electrostatic inductive relation with like elements of the coil being at substantially equal potential. I

In a telephone system, line circuits associated to.furnish a phantom circuit, and a loading coil for one of the circuits, said coil comprising sectional windings surrounding one another with adjacent layers of different sections situated at points in a circuit. at

loading coil for one of the circuits, said coil comprising windings 'and associated elements in proximity to the windings, the layers of different sections which are adjacent to the same associated element being at points in the circuits at substantially equal potential.

8. In a telephone system, linecircuits associated to furnish a phantom circuit, anda loading coil for one of the line circuits, sa d coil having sectional windings, the admittances between each section and other elements of the coil being distributed in such a symmetrical manner that like elements in the coil are at substantially equal potential with respect to the phantom current.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing Witnesses, this twenty eighth dayof January, 1910.

THOMAS SHAW.

Witnesses:

FRANK B. JEWETT, KENNETH S. JOHNSON. 

